initial commit (#4283)

Co-authored-by: Shashank Nayak <shasnayak@microsoft.com>

dev/MRTCore/packaging/MrtCore.PriGen.targets

@@ -123,7 +123,8 @@
 
   <PropertyGroup>
     <NuGetTargetFramework Condition="'$(NuGetTargetFramework)'==''">$(TargetPlatformIdentifierAdjusted),Version=v$(TargetPlatformMinVersion)</NuGetTargetFramework>
-    <RuntimeIdentifiers Condition="'$(RuntimeIdentifiers)'==''">win10-arm;win10-arm-aot;win10-arm64-aot;win10-x86;win10-x86-aot;win10-x64;win10-x64-aot</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition="$([MSBuild]::GetTargetFrameworkVersion('$(TargetFramework)')) >= 8">win-x86;win-x64;win-arm64;win-arm</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition="$([MSBuild]::GetTargetFrameworkVersion('$(TargetFramework)')) &lt; 8">win10-arm;win10-arm-aot;win10-arm64-aot;win10-x86;win10-x86-aot;win10-x64;win10-x64-aot</RuntimeIdentifiers>
     <ResolveAssemblyConflicts>true</ResolveAssemblyConflicts>
   </PropertyGroup>